This section provides background information related to the present disclosure, which is not necessarily prior art.
Coolant thermal storage systems store warm coolant, which at a cold engine start is circulated through the engine to facilitate engine warmup. While current coolant thermal storage systems are suitable for their intended use, they are subject to improvement. For example, existing thermal storage systems maintain a set coolant volume (3 liters for example) at a warmed-up temperature during periods when the engine is off (overnight for example). The coolant is kept warm in a tank with high insulating properties and/or phase change material. When the engine is turned on again, the warm coolant is allowed to circulate through the engine, aiding rapid warm-up. Thus existing thermal storage systems add coolant volume, which undesirably increases the mass of the coolant system. Packaging is also a significant challenge, because finding space under-hood for several liters of coolant storage can be virtually impossible on a modern passenger vehicle. As explained herein, the present teachings advantageously ease packaging concerns and eliminate the need to add coolant volume.